A device of this type is known for example from WO-A 93 07 362. Linear adjusting movements of the hydraulic cylinder are converted by way of an actuator into a relative rotation of the camshaft in respect to the crankshaft. Such an actuator can be positioned between a pinion and the camshaft with the pinion being driven by the crankshaft via a traction means. The actuator which is placed coaxially with respect to the pinion and the camshaft can be provided with a helical teeth or with a straight teeth, whereby these teeth cooperate with mating teeth associated with the camshaft and the pinion. When the hydraulic cylinder is operated, the actuator is axially displaced in relation to the pinion and the camshaft, whereby the helical teeth cause the camshaft to rotate relative to the pinion and thereby also relative to the crankshaft. An oil pump is driven by the camshaft of the internal combustion engine in a manner known in the art. In these conventional devices, the motor oil is empoyed as a hydraulic fluid for acting on the hydraulic cylinder. When the engine stops, the pressure in the hydraulic cylinder decreases to zero and motor oil leaks out of the hydraulic cylinder. During start of the engine, the oil pump is not yet capable of building up pressure. In the event the engine is started after it was shut down for an extended period of time, motor oil stored in the cylinder will have leaked out to such an extent that compressible gas cushions are formed in the cylinder. Consequently, the piston is able to move linearly inside the pressure chambers even if the pressure chambers are sealed off. The alternating torque transmitted by the camshaft to the actuator exerts axial forces onto the actuator caused by the described helical teeth. These axial forees cause undesirable oscillatory movements of the actuator as a consequence of the compressible gas cushions.
It is thus an object of the present invention to reliably eliminate these undesirable movements of the actuator.